hello Lester,

thank you for your kind reply.

> Do you have all of the fields in the table configured as
> 'NOT NULL'? That is - has the table been created with NOT
> NULL fields.

Yes. Here is an extract taken from the script that I use to create my
database (regarding the table involved in my message):

[snip]

CREATE DOMAIN INT_ID
AS INTEGER
NOT NULL
CHECK(VALUE > 0);

CREATE DOMAIN CH_EVENT_DESC
AS VARCHAR(50)
NOT NULL
COLLATE BETA_ISO8859_1_NOCASE;

CREATE DOMAIN DATE_EXPIRY_DATE
AS DATE
NOT NULL;

CREATE DOMAIN INT_EVENT_ALERT_DAYS
AS SMALLINT
DEFAULT 1
NOT NULL
CHECK(VALUE > 0);

CREATE DOMAIN LOGICAL
AS SMALLINT
DEFAULT 0 /* False */
NOT NULL
CHECK(VALUE IN(0, 1));

[snip]

CREATE TABLE Events(
ID_Event INT_ID,
Description CH_EVENT_DESC,
Expiry_Date DATE_EXPIRY_DATE,
Alert_Days_Before INT_EVENT_ALERT_DAYS,
Alert_Days_After INT_EVENT_ALERT_DAYS,
Event_Enabled LOGICAL);

[snip]

If I leave, for example, the field Description = NULL (it has no
default value) with CheckRequired := False, I get no error and the
NULL field is successfully posted to the database. Instead, if
CheckRequired := True, I get an IBO error message. In either case the
OnError handler of TIB_Query is *never* fired.

I forgot to mention that I'm using Firebird 1.0.2.908

> just adding the NOT NULL in the query is not the
> correct way of doing it

But I have *not* added the NOT NULL in the query. I have said that the
REQUIRED check boxes for *all* fields in the TIB_Query are grayed, so
I suppose that IBO should by-pass this test and let the database
return an error in this case.

Regards
Salvatore